It's worth noting that UUVs aren't necessarily simply "sea drones," because they are not remotely piloted in most cases.

The UUVs could be a game-changer - just like unmanned aerial vehicles (UAVs) are in the sky - by offering the naval fleets a complete operational picture. However, being the eyes in the open seas means that there is a sheer volume of water to be monitored. Providing intelligent multifunction I/O and communications capabilities is going to be a key requirement in the UUV designs.

The development and deployment of unmanned sea vehicles is rapidly expanding as the military continues to find new ways to use these intelligent machines in combat, reconnaissance, and countermine missions. Unmanned underwater vehicle (UUV) manufacturers are confronting crucial design challenges that include cost, time, size, weight and power consumption. Moreover, adding functionality to the existing I/O and communications systems, specifically to expand payload options, is a critical design consideration in unmanned sea vehicles. Enter the advanced embedded computing architectures that marry I/O and communications to mission-critical computers without expensive chassis or backplane redesign. These Ethernet communications-based systems can be configured with multiple I/O functions to meet changing payload requirements.

UUVs are growing up in the age of mounting high-sea (though shallow water threats are also an issue) threats. These vehicles are more inclined toward using COTS-based embedded systems and modular architectures amid the need for greater operational efficiency, shrinking military budgets, and time-to-mission design constraints.

The interchangeable mission-centric electronics is the hallmark of UUV design because of the constantly changing nature of naval missions – underwater search, coastal defense, sea denial, blockades, and the like – demands alternate payloads capable of executing a diverse range of applications. In these cases, a modular design architecture saves developers from integration headaches while enabling them to quickly configure the system or box according to current and future mission requirements. (Figure 1.)

In other words, UUV manufacturers can employ intelligent I/O and communications systems and subsystems, based on application-specific and standard COTS products instead of merely using single-board computers (SBCs) that could eventually lead to uncertainties about how I/O will connect in the box given the specific nature of backplane and chassis design. Moreover, the nonrecurring engineering (NRE) costs could go through the roof while system integrators are forced to requalify the box all over again.

Not surprisingly, therefore, early UUV designs like Bluefin-21 and Knifefish have relied on the embedded computing solutions with modularity and distributed interfaces while using COTS products. The advances in embedded computing, energy efficiency, sensors, robotics, and position-guidance technologies now allow the Navy to augment expensive manned systems with less-expensive and fully autonomous UUVs.

Why a modular design?

An unmanned sea vehicle is usually comprised of a multitude of off-board sensors – including compasses, Doppler velocity loggers, inertial navigation systems, and sound-velocity sensors – that carry out search, avoid, or follow operations in a highly automated manner. First and foremost, the vehicle requires a stable control system to perform vehicle autonomy, mission planning and execution, payload data management, and other processing-centric tasks.

Next, UUVs are required to understand features in their environment so they can intelligently detect and classify items and then respond to sensor data in an automated manner. In this realm, the vehicle’s control system, based on low-power and high-performance processors, reacts to physical or tactical tasks using appropriate payloads in close collaboration with monitoring sensors.

That complexity just shows how crucial the connection is between the control or processor part and the sensors parts. The ability to read and simulate that data simultaneously requires robust processing and I/O capabilities, and is a huge requirement in the UUV design.

A modular and highly adaptive architecture (Figure 2) allows UUV designers to add a controller board to the existing system and connect it to the Ethernet or CAN bus; the controller board will connect to whatever payload UUV manufacturers want to support. It has to be a flexible and scalable design solution because the main system cannot be changed significantly.

Figure 2: Modular architectures enable UUV designers to select suitable COTS components for specific payloads, add them to the subsystem, and connect to the Ethernet network.

(Click graphic to zoom by 1.8x)

In contrast, creating a new box with all the functionalities outlined above could add to design complexities and cause additional NRE costs. Take the case of adding a new mission computer for a new payload: To begin with, a designer might not know how to interface a legacy sensor/transducer with the new board. The designer might then have to requalify the whole box, which could take months.

Intelligent I/O functions

The UUVs could be a game-changer – just like unmanned aerial vehicles (UAVs) are in the sky – by offering the naval fleets a complete operational picture. However, being the eyes in the open seas means that there is a sheer volume of water to be monitored. Providing intelligent multifunction I/O and communications capabilities is going to be a key requirement in the UUV designs.

The I/O functionality is specifically targeted on the payload that UUVs have to carry. For instance, if a UUV has to handle I/O functionality from Ethernet to synchro/resolver or Ethernet to CANbus, it is imperative that the I/O devices can be easily configured with multiple functions. Another example: Take the case of a UUV that needs to monitor temperature using resistance temperature detector (RTD) channels.

In this instance, a COTS modular and configurable board enables UUV designers to quickly create an application for this new payload. A configurable I/O module is flexible enough to accommodate different payloads with a diverse range of I/O devices. Furthermore, for a new payload on the UUV, a systems integrator can simply add a prequalified board to the box that has already been qualified and tested.

The UAV design redux

It’s worth noting that UUVs aren’t necessarily simply “sea drones,” because they are not remotely piloted in most cases. Unlike UAVs, which are inherently well-placed to pluck radio signals from the air, sea water is opaque for radio communications; moreover, acoustic signals travel slower than wireless signals.

The fact that UUVs are fully autonomous and highly automated calls for extremely robust and reliable electronics based on the fundamental building blocks: communications, power management, data management, and storage. At the same time, however, the anatomy of UUVs is quite similar to the UAV design blueprints. This reality is a welcome relief for the Navy engineers. UAVs set a precedent by using COTS components and modular architectures and now UUV designers are following suit to enable SWaP-C concerns.

The use of application-specific standard COTS systems like NAI’s NIU1A (Figure 3) enables engineers to bypass costly box redesigns by using multifunction I/O and communications to Ethernet data concentrators instead.

Figure 3: Nanosized subsystem with Intelligent I/O capability connects to existing platform Ethernet networks, making data available to any system on the network.

(Click graphic to zoom by 1.9x)

Apparently, UUVs are reshaping the basic underpinnings of sea warfare. The U.S. Navy has acknowledged that UUVs are going to be a force multiplier for its regular fleets and has allocated a significant amount of funds for the expansion of its UUV fleet in the 2016 budget. Now it’s up to the design engineers to show that they can create innovative electronic systems without making SWaP-C tradeoffs.

Lino Massafra is the VP of sales and marketing at North Atlantic Industries, Inc. (NAI) in Bohemia, New York. He has been with the company since 2008 and has led the global sales team in the areas of embedded electronics and computing systems for sense-and-response military and aerospace applications. He earned his Bachelor of Science and Master of Science degrees in electrical engineering from Manhattan College in New York.